[meteorite-list] Inside NASA's Plan to Catch an Asteroid

[Ron Baalke]

http://www.space.com/20612-nasa-asteroid-capture-mission-explained.html

Inside NASA's Plan to Catch an Asteroid (Bruce Willis Not Required)
by Mike Wall
space.com
10 April 2013

President Barack Obama's 2014 federal budget request, which was released 
Wednesday (April 10), gives NASA $105 million to jump-start a program that 
would snag an asteroid and park it near the moon. Astronauts would then 
visit the space rock using the agency's Space Launch System rocket and 
Orion capsule, perhaps as early as 2021.

"This mission represents an unprecedented technological feat that will lead 
to new scientific discoveries and technological capabilities and help protect 
our home planet," NASA chief Charles Bolden said in a statement. 

The space agency is still working out how exactly to pull off the mission, 
which officials are calling the "Asteroid Initiative" or "Asteroid Retrieval 
and Utilization Mission" at the moment. But a few things are already clear.

For starters, the probe that will chase down and capture the 25-foot (8 meters) 
or so asteroid will be unmanned. And it will be powered by solar electric 
propulsion, which generates thrust by accelerating charged particles called ions.

Ion thrusters have been used on other NASA probes, including Dawn, which 
recently spent a year orbiting the huge asteroid Vesta before departing for the 
dwarf planet Ceres. But engineers will need to develop an advanced version for the 
Asteroid Initiative craft, since it will be towing a 500-ton space rock 
over millions of miles.

"This mission accelerates our technology development activities in high-powered 
solar electric propulsion," Michael Gazarik, NASA Associate Administrator for 
Space Technology, said in a statement.

Still, it may take several years for the probe to meet up with the asteroid. 
The spacecraft will then envelop the space rock with a bag of sorts, as 
a new video animation of NASA's Asteroid Initiative mission depicts, and 
de-spin the rock, likely using thrusters.

The asteroid will then be towed to a "stable orbit in the Earth-moon system where 
astronauts can visit and explore it," NASA officials wrote in a mission description 
Wednesday.

These visits will be made possible by Orion and the Space Launch System, which 
are slated to begin flying crews together by 2021. The NASA animation 
shows astronauts aboard Orion meeting up with the space rock, which the 
retrieval probe is still holding onto.

In the video, the astronauts spacewalk their way over to the asteroid, accessing it 
by unwrapping a small section of the bag. They grab some pieces using a hammer and 
other tools, then come home with the samples in an ocean splashdown.

The overall asteroid-retrieval idea is similar to one proposed by researchers based 
at Caltech's Keck Institute for Space Studies in Pasadena. In a feasibility study 
published last year, the Keck team estimated the total cost of robotic capture and 
return at $2.6 billion.

NASA hasn't released its own cost estimates yet, but agency officials think they can 
get it done for less than that.

"The Keck study didn't take into account all the activities we already have 
going on in our base, so we wouldn't need $2.6 billion in new money," 
NASA chief financial officer Elizabeth Robinson said during a press conference 
Wednesday.

The Keck team also focused on grabbing a carbonaceous chondrite, 
she added. These asteroids are compositionally diverse, full of complex 
organic molecules, metals and volatile materials like water.

But carbonaceous chondrites also tend to be found farther away than other types of 
near-Earth asteroids, Robinson said, making their retrieval more time-consuming and 
expensive. At this point, NASA isn't so particular about the space rock 
it hopes to target.

"For those two reasons, we think that the price is likely to come in - of 
new money, new investment - at below that [$2.6 billion]," Robinson said.